{"api_version":"1","generated_at":"2026-09-19T06:02:35+00:00","cve":"CVE-2026-93197","urls":{"html":"https://cve.report/CVE-2026-93197","api":"https://cve.report/api/cve/CVE-2026-93197.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-93197","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-93197"},"summary":{"title":"memcg: move LRU size accounting on reparenting instead of copying it","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nmemcg: move LRU size accounting on reparenting instead of copying it\n\nWhen a memory cgroup is offlined its LRU folios are reparented to the\nparent.  lruvec_reparent_lru() splices the child's lists into the\nparent's and credits the parent with the child's per-zone\nlru_zone_size[], but never clears the child's copy, so the size is\ncopied rather than moved.  lru_gen_reparent_memcg() does the same for\nMGLRU.\n\nThe parent is left correct, credited with exactly the folios it took\nover.  The stale value sits on the child and nothing will correct it:\nfolio->memcg_data now resolves to the parent, so every later\nupdate_lru_size() for those folios goes there.\n\nDying cgroups are not freed immediately and mem_cgroup_iter() still\nwalks them, so shrink_lruvec() keeps being called on them.\nget_scan_count() reads the phantom counter through lruvec_lru_size() and\nthe scan loop then grinds through nr[] in SWAP_CLUSTER_MAX steps against\nan empty list, for as long as the dead cgroup lives.  Under MGLRU the\nMGLRU scanner runs instead, but count_shadow_nodes() sums all of\nNR_LRU_LISTS through lruvec_lru_size() and over-budgets the shadow node\nlimit just the same.\n\nOn one 251 GiB host a sweep of every mz->lru_zone_size[] found 380\ncounters describing folios on no list at all: 124777314 pages, 476 GiB,\n1.89x the machine's RAM, across 57 cgroups.  All were on memcgs with\nCSS_DYING set and CSS_ONLINE clear, and parent/child pairs reported\nbyte-identical sizes.\n\nLRU_UNEVICTABLE needs its size moved too.  Its list is deliberately not\nspliced because lruvec_init() poisons the head - the unevictable LRU is\nimaginary and folios are never threaded on it - but the size is kept by\nlruvec_add_folio()/lruvec_del_folio() and those folios account to the\nparent from here on.\n\nThis depends on commit bf4ade7dbd76 (\"memcg: keep folio's objcg same as\nits node\") and must not be backported ahead of it.  Without that\ninvariant a folio's objcg can belong to another node, so a folio already\nspliced onto the parent's list can still resolve to the child's lruvec\nuntil the objcg's node is reparented in a later iteration of\nmemcg_reparent_objcgs(); clearing the child's counter early then lets\nlruvec_del_folio() underflow it and trip the WARN_ONCE()/VM_BUG_ON() in\nmem_cgroup_update_lru_size().","state":"PUBLISHED","assigner":"Linux","published_at":"2026-09-17 17:18:15","updated_at":"2026-09-17 17:18:15"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/0e0ac326c511d514817cc7b6d7741afd59098ce2","name":"https://git.kernel.org/stable/c/0e0ac326c511d514817cc7b6d7741afd59098ce2","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/007bc1842317bb99f5f6205afede940f951674c2","name":"https://git.kernel.org/stable/c/007bc1842317bb99f5f6205afede940f951674c2","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-93197","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-93197","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 07a6e9a2c199fed361f528781284d56771d0016f 007bc1842317bb99f5f6205afede940f951674c2 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 07a6e9a2c199fed361f528781284d56771d0016f 0e0ac326c511d514817cc7b6d7741afd59098ce2 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 7.1","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.1 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.6 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3-rc1 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"93197","cve":"CVE-2026-93197","epss":"0.001760000","percentile":"0.074400000","score_date":"2026-09-18","updated_at":"2026-09-19 00:06:17"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["mm/folio.c","mm/vmscan.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"007bc1842317bb99f5f6205afede940f951674c2","status":"affected","version":"07a6e9a2c199fed361f528781284d56771d0016f","versionType":"git"},{"lessThan":"0e0ac326c511d514817cc7b6d7741afd59098ce2","status":"affected","version":"07a6e9a2c199fed361f528781284d56771d0016f","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["mm/folio.c","mm/vmscan.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"7.1"},{"lessThan":"7.1","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.6","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3-rc1","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.6","versionStartIncluding":"7.1","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3-rc1","versionStartIncluding":"7.1","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nmemcg: move LRU size accounting on reparenting instead of copying it\n\nWhen a memory cgroup is offlined its LRU folios are reparented to the\nparent.  lruvec_reparent_lru() splices the child's lists into the\nparent's and credits the parent with the child's per-zone\nlru_zone_size[], but never clears the child's copy, so the size is\ncopied rather than moved.  lru_gen_reparent_memcg() does the same for\nMGLRU.\n\nThe parent is left correct, credited with exactly the folios it took\nover.  The stale value sits on the child and nothing will correct it:\nfolio->memcg_data now resolves to the parent, so every later\nupdate_lru_size() for those folios goes there.\n\nDying cgroups are not freed immediately and mem_cgroup_iter() still\nwalks them, so shrink_lruvec() keeps being called on them.\nget_scan_count() reads the phantom counter through lruvec_lru_size() and\nthe scan loop then grinds through nr[] in SWAP_CLUSTER_MAX steps against\nan empty list, for as long as the dead cgroup lives.  Under MGLRU the\nMGLRU scanner runs instead, but count_shadow_nodes() sums all of\nNR_LRU_LISTS through lruvec_lru_size() and over-budgets the shadow node\nlimit just the same.\n\nOn one 251 GiB host a sweep of every mz->lru_zone_size[] found 380\ncounters describing folios on no list at all: 124777314 pages, 476 GiB,\n1.89x the machine's RAM, across 57 cgroups.  All were on memcgs with\nCSS_DYING set and CSS_ONLINE clear, and parent/child pairs reported\nbyte-identical sizes.\n\nLRU_UNEVICTABLE needs its size moved too.  Its list is deliberately not\nspliced because lruvec_init() poisons the head - the unevictable LRU is\nimaginary and folios are never threaded on it - but the size is kept by\nlruvec_add_folio()/lruvec_del_folio() and those folios account to the\nparent from here on.\n\nThis depends on commit bf4ade7dbd76 (\"memcg: keep folio's objcg same as\nits node\") and must not be backported ahead of it.  Without that\ninvariant a folio's objcg can belong to another node, so a folio already\nspliced onto the parent's list can still resolve to the child's lruvec\nuntil the objcg's node is reparented in a later iteration of\nmemcg_reparent_objcgs(); clearing the child's counter early then lets\nlruvec_del_folio() underflow it and trip the WARN_ONCE()/VM_BUG_ON() in\nmem_cgroup_update_lru_size()."}],"providerMetadata":{"dateUpdated":"2026-09-17T16:12:19.776Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/007bc1842317bb99f5f6205afede940f951674c2"},{"url":"https://git.kernel.org/stable/c/0e0ac326c511d514817cc7b6d7741afd59098ce2"}],"title":"memcg: move LRU size accounting on reparenting instead of copying it","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-93197","datePublished":"2026-09-17T16:12:19.776Z","dateReserved":"2026-09-17T16:02:15.092Z","dateUpdated":"2026-09-17T16:12:19.776Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-17 17:18:15","lastModifiedDate":"2026-09-17 17:18:15","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"93197","Ordinal":"1","Title":"memcg: move LRU size accounting on reparenting instead of copyin","CVE":"CVE-2026-93197","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"93197","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nmemcg: move LRU size accounting on reparenting instead of copying it\n\nWhen a memory cgroup is offlined its LRU folios are reparented to the\nparent.  lruvec_reparent_lru() splices the child's lists into the\nparent's and credits the parent with the child's per-zone\nlru_zone_size[], but never clears the child's copy, so the size is\ncopied rather than moved.  lru_gen_reparent_memcg() does the same for\nMGLRU.\n\nThe parent is left correct, credited with exactly the folios it took\nover.  The stale value sits on the child and nothing will correct it:\nfolio->memcg_data now resolves to the parent, so every later\nupdate_lru_size() for those folios goes there.\n\nDying cgroups are not freed immediately and mem_cgroup_iter() still\nwalks them, so shrink_lruvec() keeps being called on them.\nget_scan_count() reads the phantom counter through lruvec_lru_size() and\nthe scan loop then grinds through nr[] in SWAP_CLUSTER_MAX steps against\nan empty list, for as long as the dead cgroup lives.  Under MGLRU the\nMGLRU scanner runs instead, but count_shadow_nodes() sums all of\nNR_LRU_LISTS through lruvec_lru_size() and over-budgets the shadow node\nlimit just the same.\n\nOn one 251 GiB host a sweep of every mz->lru_zone_size[] found 380\ncounters describing folios on no list at all: 124777314 pages, 476 GiB,\n1.89x the machine's RAM, across 57 cgroups.  All were on memcgs with\nCSS_DYING set and CSS_ONLINE clear, and parent/child pairs reported\nbyte-identical sizes.\n\nLRU_UNEVICTABLE needs its size moved too.  Its list is deliberately not\nspliced because lruvec_init() poisons the head - the unevictable LRU is\nimaginary and folios are never threaded on it - but the size is kept by\nlruvec_add_folio()/lruvec_del_folio() and those folios account to the\nparent from here on.\n\nThis depends on commit bf4ade7dbd76 (\"memcg: keep folio's objcg same as\nits node\") and must not be backported ahead of it.  Without that\ninvariant a folio's objcg can belong to another node, so a folio already\nspliced onto the parent's list can still resolve to the child's lruvec\nuntil the objcg's node is reparented in a later iteration of\nmemcg_reparent_objcgs(); clearing the child's counter early then lets\nlruvec_del_folio() underflow it and trip the WARN_ONCE()/VM_BUG_ON() in\nmem_cgroup_update_lru_size().","Type":"Description","Title":"memcg: move LRU size accounting on reparenting instead of copyin"}]}}}